Long before that, corals grew in the sea located around upper Michigan when atmospheric CO2 levels were > 2000 ppm. Sadly, the corals went extinct, but fossilized samples abound.http://en.wikipedia.org/wiki/Petoskey_stone

I suppose this is how it would look like at the end of summer. Should there not be more multi year sea ice in the Arctic ocean? If not it would be full with drowning and hungry polar bears.
When did the first polar bears settle in the Hudson bay region.?

While no one was actually around 20K years ago I do think that we can determine global temps and estimate ice coverage. Just like we know the ocean levels were 300 to 400 feet lower during this days. I am not sure anyone knows exactly how CO2 and everything interacts, but certainly there is more to learn. Holds heat global warming or reflects cooling? We do know the Earth goes through cycles and they will continue. Areas that were tropical are now frozen or are deserts, etc.

Nature is 98% to 99% responsible and man maybe 1%. CO2 levels were much higher before man and I am more worried about a global freeze than warming. I understand the polar bear population is up, so at least they like the ice. On a lighter side, we can clone some wooly mammoths and get ready for the new ice age.

Good point TNSteve, we have a lot to learn. I saw a NatGeo how the earth was made film. It described the entire planet as ice before liquid oceans were to appear. Then over millions of years the cycle of 4 ice ages took place. The last being the one we credit for so many land, lake and ocean features we see today. Unanswered were the number of SUVs it took to melt all the ice so many times?